1. Field of the Invention
The present invention relates to a method of inspecting whether a printed board is appropriately supported in an electric-component mounting apparatus.
2. Discussion of Related Art
There is known an electric-component (EC) mounting apparatus which takes, with an image taking device, an image of a reference mark provided on a printed board (e.g., printed wiring board) which is supported by a supporting device, determines, based on the taken image of the reference mark, a position of the printed board supported by the supporting device, and modifies a prescribed amount of movement of an EC that is needed to position the EC at a position right above an EC-mount location on the printed board. However, the conventional apparatus determines, on the assumption that the printed board is appropriately supported by the supporting device, a positional error of the printed board from a prescribed position thereof, and modifies, based on the determined positional error of the printed board, the prescribed amount of movement of EC that is needed to position the EC at the position right above the EC-mount location on the printed board and mount the EC at the EC-mount location.
Therefore, even in the case where the magnitude of actual positional error of the printed board exceeds a permissible error range which is proper for the supporting device and/or the image taking device, the conventional apparatus may mount one or more ECs on the printed board. In addition, in the case where the actual positional error of printed board is great, a great error or errors tend to occur when the positional error is determined or calculated and/or when the positional error is corrected. More specifically described, if the actual position of the printed board is greatly deviated from the prescribed position thereof, then the image of the reference mark that should be taken around the center of view field of the image taking device is, in fact, taken in a peripheral portion of the view field. However, generally, the image taking device (e.g., camera) tends to have a greater distortion in the peripheral portion of view field (e.g., lens) thereof. Therefore, a greater error tends to occur when the positional error of the printed board is calculated based on the reference-mark image taken by the image taking device. Moreover, if the prescribed amount of movement of EC is greatly modified based on the great positional error of printed board, a great error tends to be included in the modified amount of movement of EC, so that the EC may be mounted, with insufficient accuracy, on the printed board (e.g., printed circuit board).
In addition, if the magnitude of actual positional error of the printed board exceeds the above-indicated permissible error range, then abnormality may have occurred to the EC mounting apparatus itself, or the printed board currently supported by the supporting device may differ from the prescribed sort of printed board. The abnormality with the EC mounting apparatus itself may be such that a board conveyor (i.e., a pair of conveyor belts) has failed to adjust appropriately its board-convey width depending upon the size of current sort of printed boards and accordingly the printed board has been conveyed in an unstable state, or such that the overall shape of the printed board has been deformed because the relative position between the printed board and the supporting device in a vertical direction is not appropriate.
FIGS. 6A, 6B, and 6C show a case where an EC 206 is mounted on a second, upper surface 204 of a printed board 200 having, in addition to the second surface 204, a first, lower surface 202 having an EC 206 already mounted thereon. A board supporting device 208 includes at least one board support member 209, and is moved upward from its initial position shown in FIG. 6A, so that the board support member 209 engages the first surface 202 of the printed board 200, as shown in FIG. 6C, and thereby supports the board 200. In this case, the conventional EC mounting apparatus may suffer from the above-described problems. If an actual position of the printed board 200 is largely deviated from its prescribed position, the board support member 209 interferes with the EC 206 already mounted on the first surface 202, as shown in FIG. 6B. Consequently the EC 206 mounted on the first surface 202 is removed from the surface 202, as shown in FIG. 6C, or is moved out of position or changed in its posture on the surface 202, because it has been just temporarily fixed to the surface 202 with creamed solder or adhesive. Even if the EC 206 may be mounted on the second surface 204 of the printed board 200 whose first surface 202 has had the above-indicated abnormality, the printed board 200 will be discarded as a defective product. Therefore, the one or more ECs 206 mounted on the second surface 204 and the time needed to mount the ECs 206 on the second surface 204 are used to waste.
When the EC 206 already mounted on the first surface 202 is interfered with by the board support member 209, the EC 206 may not be removed off the first surface 202 or be moved out of position. In this case, however, the printed board 200 is supported by the board supporting device 208 in the state in which the EC 206 is sandwiched between the board 200 and the support member 209, so that the board 200 is pushed up by the EC 206 and its shape is deformed. In this state, it is difficult to mount appropriately the EC or ECs 206 on the second surface 204 of the board 200. Eventually, the board 200 will probably be defective. These problems have been more and more serious because of a recent demand to increase the density of mounting of ECs.
The present invention provides a board-supporting inspecting method, an electric-component mounting apparatus, and an inspecting-program recording medium which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (16). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided a method of inspecting whether a printed board is appropriately supported by a supporting device, when a holding device holding an electric component mounts the electric component on the printed board supported by the supporting device, the method comprising the steps of taking, with an image taking device, an image of at least one prescribed detection portion of the printed board supported by the supporting device, and judging, based on image data representing the taken image of the detection portion, whether the printed board is appropriately supported by the supporting device. The image taking device can be regarded as a sort of detecting device which detects the prescribed or predetermined detection portion of the printed board.
In a conventional EC mounting method, a relative position of the printed board relative to the EC holding device is determined based on a relative position of a reference mark, as a sort of prescribed detection portion of the printed board, relative to the image taking device, and an amount of relative movement between the EC holding device and the board supporting device is modified based on the determined position of the printed board, so that the EC held by the holding device is accurately mounted on the printed board supported by the board supporting device. In contrast thereto, the present inspecting method judges, based on the taken image of the detection portion of the printed board, whether or not the printed board is appropriately supported by the board supporting device.
Taking an image of a reference mark of a printed board before an EC is mounted on the printed board has been widely practiced. Since the present method can inspect, based on information obtained by taking the image of the reference mark, whether the printed board is appropriately supported, the present method can be easily carried out on a conventional EC mounting apparatus. In addition, since the present method does not need any additional steps or actions of the mounting apparatus, the present method can avoid the lowering of operation efficiency of the mounting apparatus.
The present method can inspect whether the printed board is appropriately supported, before one or more ECs are mounted on the printed board. If whether or not to carry out the EC mounting operation is decided based on the result of the inspection, it is possible to prevent the wasteful use of ECs and improve the operation efficiency. For example, if the result of the inspection is positive, it is possible to allow the current EC mounting operation to continue; and if the result is negative, it is possible to inform an operator of the negative result so that the operator can make his or her own judgment. Alternatively, the EC mounting apparatus may be controlled by a control device to find one or more causes of the abnormality with the printed board.
The prescribed detection portion of the printed board may be a prescribed portion of a circuit pattern of a printed wiring board or a printed circuit board each as the printed board, or may be a reference mark (e.g., a fiducial mark) which is provided on at least one of opposite surfaces of the printed board.
(2) According to a second feature of the present invention that includes the first feature (1), the step of taking comprises taking an image of at least one reference mark provided on the printed board supported by the supporting device, and the step of judging comprises determining, based on image data representing the taken image of the reference mark, at least one actual position of the printed board supported by the supporting device; and judging, based on the determined actual position of the printed board, whether the printed board is appropriately supported by the supporting device.
The at least one actual position of the printed board may be at least one of a position of the board in an X direction parallel to the board, a position of the board in a Y direction parallel to the board and perpendicular to the X direction, and a position of the board in a Z direction perpendicular to the X and Y directions.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the inspecting method further comprises the step of outputting, with an output device, information representing a result of the judgment, such that the output information is recognizable by an operator.
The output device may output both a positive and a negative result of the judgment, or may output only the negative result. Even in the former case, it is preferred that the negative result be output in a more distinct manner than a manner in which the positive result is output. Moreover, it is possible to output, in addition to the result of the current judgment, the accumulated results of the past judgments and/or the frequency at which the negative results are obtained during the current, continuous operation.
Since the present inspecting method can timely inform the operator of the result of judgment, the operator can quickly respond to the abnormality with the printed board.
(4) According to a fourth feature of the present invention that includes the third feature (3), the step of outputting comprises outputting information representing a negative result of the judgment.
The present method can allow, when the result of judgment is positive, the current EC mounting operation to continue and output, when the result is negative, information indicating the result is negative, so that the operator can make his or her own inspection or judgment.
(5) According to a fifth feature of the present invention that includes any one of the first to fourth features (1) to (4), the inspecting method further comprises the step of, when it is judged that the printed board is not appropriately supported by the supporting device, stopping a mounting operation in which the holding device will mount the electric component on the printed board judged as being not appropriately supported by the supporting device.
The present method stops, when the result of judgment is negative, the EC mounting operation, thereby preventing the EC from being mounted on the printed board judged as being not appropriately supported by the supporting device. Thus, the present method can prevent wasteful use of ECs and wasteful EC mounting operations. Then, the operator may check the printed board and/or the EC mounting apparatus (e.g., the board supporting device) and decide, based on the result of checking, whether to allow the EC mounting operation or to discharge the current printed board from the board supporting device. Alternatively, the EC mounting apparatus may automatically re-adjust each of the elements thereof, as described below.
For example, if the abnormality with the printed board is caused by inappropriate adjustment of the board-convey width of a board conveying device of the mounting apparatus, or by inappropriate adjustment of the height position of the printed board supported by the board supporting device, the EC mounting apparatus may automatically re-adjust the board-convey width or the height position because the inappropriate board-convey width or the inappropriate height position can be corrected by the re-adjustment thereof. If a positive result is obtained when the present inspecting method is carried out again, it is possible to resume the EC mounting operation; and if a negative result is obtained, it is possible to output information indicative of the second negative result, thereby requesting the operator to make his or her re-judgment. Even though the printed board may be placed in the state appropriately supported by the supporting device as a result of automatic re-adjustment, the EC mounting apparatus may, however, have an abnormality, if the automatic re-adjustments are frequently carried out. In this case, it is preferred to output information indicative of the frequent re-adjustments, so that the operator can find one or more causes of the frequent re-adjustments.
(6) According to a sixth feature of the present invention that includes any one of the second to fifth features (2) to (5), the step of judging comprises judging whether the printed board is appropriately supported by the board supporting device, based on at least one actual position of the reference mark in the image taken by the image taking device, and at least one prescribed position of the reference mark as at least one reference position thereof.
The prescribed position of the reference mark may be any position in the field of view of the image taking device, preferably at the center of the view field.
(7) According to a seventh feature of the present invention that includes the sixth feature (6), the step of judging comprises prescribing a two-dimensional permission range as the reference position of the reference mark, and judging whether the actual position of the reference mark in the taken image falls within the prescribed permission range.
The prescribed permission range may be a circular or square area whose center coincides with the X and Y coordinates of the prescribed position as the reference position of the reference mark, or may have a shape having different dimensions in the X and Y directions.
(8) According to an eighth feature of the present invention that includes any one of the first to seventh features (1) to (7), the step of taking comprises taking, when the holding device mounts the electric component on one of opposite surfaces of the printed board the other surface of which has at least one electric component already mounted thereon and is engaged with the supporting device, the image of the detection portion of the one surface of the printed board.
The present inspecting method inspects whether the first surface of the printed board is appropriately supported, in the state in which the first surface has one or more ECs already mounted thereon. Therefore, the present method can monitor or judge whether the supporting device interferes with the EC or ECs mounted on the first surface of the printed board.
As explained previously, the EC or ECs are just temporarily fixed to the first surface of the printed board, with, e.g., creamed solder. In this state, one or more ECs are mounted on the second surface of the same board. Therefore, if the board is supported at an incorrect position by the supporting device, the supporting device may interfere with the EC or ECs temporarily fixed to the first surface, so that the EC or ECs may fall down off the first surface. Thus, when the present method judges that the board is not appropriately supported before one or more ECs are mounted on the second surface, it is preferred to stop the current EC mounting operation and request the judgment of the operator, to the re-adjustment of the element or elements of the EC mounting apparatus. For example, the operator can check the first surface of the board and decide, based on the result of checking, whether to resume the current EC mounting operation or to discharge the current board from the supporting device.
(9) According to a ninth feature of the present invention that includes the eighth feature (8), the supporting device comprises at least one support member having at least one two-dimensional support spot which supports the printed board by engaging the other surface thereof at at least one support location prescribed for a sort of the printed board, and the step of prescribing comprises prescribing the permission range which assures that the support member of the supporting device does not interfere with the electric component already mounted on the other surface of the printed board.
Since the prescribed permission range assures that the support member does not interfere with any ECs already mounted on the other surface of the printed board, the present inspecting method can monitor or judge whether the support member interferes with the EC or ECs mounted on the other surface of the printed board. In the case where the supporting device includes a plurality of support members, the permission range is so prescribed as to assure that every support member does not interfere with any ECs already mounted on the other surface of the printed board.
(10) According to a tenth feature of the present invention that includes any one of the first to ninth features (1) to (9), the step of judging comprises judging whether the printed board is appropriately supported by the supporting device in each of a first direction and a second direction which are parallel to the printed board supported by the supporting device and are perpendicular to each other.
The first and second directions may be an X-axis direction and a Y-axis direction, respectively, on an X-Y coordinate system parallel to the printed board.
(11) According to an eleventh feature of the present invention that includes any one of the first to tenth features (1) to (10), the step of judging comprises judging whether the printed board is appropriately supported by the supporting device in a direction perpendicular to the printed board supported by the supporting device.
The direction perpendicular to the printed board may be a Z direction perpendicular to the X-axis direction and Y-axis direction on the X-Y coordinate system parallel to the printed board.
(12) According to a twelfth feature of the present invention that includes the eleventh feature (11), the step of judging comprises judging whether a rate of change of respective optical characteristic values at respective positions on a line intersecting an edge line of the taken image of the detection portion, with respect to a direction along the line, is greater than a threshold value and, if a negative judgment is made, judging that the printed board is not appropriately supported by the supporting device in the direction perpendicular to the printed board. The rate of change may be the greatest one of respective rates of change of the respective optical characteristic values at the respective positions on the intersecting line, as calculated in the direction along the intersecting line. The intersecting line may be a straight line prescribed for an edge line of a reference image of the prescribed portion of the printed board.
(13) According to a thirteenth feature of the present invention, there is provided a method of inspecting whether a printed board is appropriately supported by a supporting device, when a holding device holding an electric component mounts the electric component on the printed board supported by the supporting device, the method comprising the steps of detecting a height position of at leas one prescribed detection portion of the printed board supported by the supporting device, and judging, based on the detected height position of the detection portion, whether the printed board is appropriately supported by the supporting device.
(14) According to a fourteenth feature of the present invention, there is provided an apparatus for mounting at least one electric component on a printed board, comprising a supporting device which supports the printed board by engaging a lower surface thereof; a holding device which holds the electric component and mounts the electric component on the printed board supported by the supporting device; an image taking device which takes an image of at least one detection portion of the printed board supported by the supporting device; and a control device which controls the supporting device, the holding device,and the image taking device to mount the electric component on the printed board, the control device comprising a judging portion which judges, based on image data representing the image of the detection portion taken by the image taking device, whether the printed board is appropriately supported by the supporting device.
The present EC mounting apparatus can carry out the inspecting method according to the first feature (1), and may employ any one of the above-described second to twelfth features (2) to (12).
(15) According to a fifteenth feature of the present invention that includes the fourteenth feature (14), the image taking device takes an image of at least one reference mark which is provided on the printed board supported by the supporting device, the control device further comprises an actual-position determining portion which determines, based on image data representing the image of the reference mark taken by the image taking device, at least one actual position of the printed board supported by the supporting device, and the judging portion judges, based on the determined actual position of the printed board, whether the printed board is appropriately supported by the supporting device.
(16) According to a sixteenth feature of the present invention, there is provided a recording medium in which an inspecting program is recorded such that the inspecting program is readable by a computer to cooperate with an image taking device to inspect whether a printed board is appropriately supported by a supporting device in an electric-component mounting apparatus in which a holding device holding an electric component mounts the electric component on the printed board which is supported by the supporting device, at least one of the holding device holding the electric component and the supporting device supporting the printed board being movable relative to the other of the holding device and the supporting device, the inspecting program comprising the steps of taking, with the image taking device, an image of at least one detection portion of the printed board supported by the supporting device, and judging, based on image data representing the taken image of the detection portion, whether the printed board is appropriately supported by the supporting device
If the computer of the EC mounting apparatus reads the inspecting program recorded in or on the present recording medium, the apparatus can carry out the inspecting method according to the first feature (1). The inspecting program recorded in the present recording medium may employ any one of the above-described second to twelfth features (2) to (12).
(17) According to a seventeenth feature of the present invention that includes the sixteenth feature (16), the step of taking comprises taking an image of at least one reference mark which is provided on the printed board supported by the supporting device, the inspecting program further comprises the step of determining, based on image data representing the taken image of the reference mark, at least one actual position of the printed board supported by the supporting device, and the step of judging comprises judging, based on the determined actual position of the printed board, whether the printed board is appropriately supported by the supporting device.